[OOC] Add NaryJoinOOCPrimitive and Generic Join

[janniklinde]

This patch introduces an OOC nary join primitive, targeting the ifelse statement. Further, we make the join operation generic to support arbitrary SpillableObjects.

Assisted-by: AI

[codecov]

Codecov Report

❌ Patch coverage is 72.00000% with 91 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.41%. Comparing base (beb1fe3) to head (4c399b3).

Files with missing lines	Patch %	Lines
...s/runtime/ooc/primitives/NaryJoinOOCPrimitive.java	76.39%	25 Missing and 13 partials ⚠️
...apache/sysds/runtime/ooc/util/StateTableUtils.java	51.42%	13 Missing and 4 partials ⚠️
.../org/apache/sysds/runtime/ooc/cache/OOCFuture.java	55.55%	13 Missing and 3 partials ⚠️
...untime/instructions/ooc/TernaryOOCInstruction.java	35.00%	9 Missing and 4 partials ⚠️
...sysds/runtime/ooc/primitives/JoinOOCPrimitive.java	90.90%	2 Missing and 2 partials ⚠️
...org/apache/sysds/runtime/ooc/store/StateTable.java	50.00%	2 Missing ⚠️
...he/sysds/runtime/ooc/cache/packed/PackedBlock.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               main    #2594    +/-   ##
==========================================
  Coverage     71.41%   71.41%            
- Complexity    50463    50506    +43     
==========================================
  Files          1630     1631     +1     
  Lines        195661   195928   +267     
  Branches      38135    38178    +43     
==========================================
+ Hits         139731   139928   +197     
- Misses        44964    45012    +48     
- Partials      10966    10988    +22     

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